I called Verizon prior to our Fantasy Western Caribbean cruise to ask about data charges, as I needed to check some e-mails while gone. I paid $25 for 100 MB of data, which in the typical world, should be plenty. Haven't seen my bill yet to know what might actually show up, but I was able to check, send and receive e-mails in Cozumel with no problem. Tried it in Grand Cayman and didn't have as much luck ("searching...searching...searching...").
PP's prices on sending and receiving texts is what they also told me, but I did not do any texting. When you get "over the line", Verizon sends a few texts reminding you of what, if any, plans you have to cover international issues. This basically serves as a gentle reminder to put your phone in airplane mode!
I made no calls, as there did not seem to be any special deal for those and, as per above, there can be other hidden charges for those.
In short, just call Verizon to see what might already be included in your plan or what options you might have for a week at sea. I told them I just wanted the $25 for the month during which my cruise sailed, and they have promised to take it back off after that month. We'll see!